Process for the treatment of paper mill effluent



P. HODGES Aug. 14, 1945.

PROCESS FOR THEV TREATMENT OF PAPER MILL vEFFLUENT Filed Jan. 19, 1942 NL. ZMS 4.1.1

Patented Aug. 14V, 1945 l UNITED STATES PAraNr or-'Fics PROCESS FR THE-TREATMENT OF PAPER y MLL EFFLUENT reni Hedges, crossen, Ark.; Lmiem` F. Hedges edministratrix of said Paul Hodges, deceased Application January 19, 1942, Serial No. 427,378

(Cl. 20-2l -9 Claims.

My invention relates tothe treatment of the eiiiuent from alkaline or kraft pulp or paper mills,

causesthe lignin, fatty acids, and resins of the black liquor to separate out, thus clarifying and purifying the emuent and rendering it safe for animal and plant life.`

A still further object of my invention is to provide a process for the treatment of the black liquor containing eiiluent from a vsulphate process paper mill which shall be effective to clarify the eiiiuent, remove harmful compounds therefrom, and which shall include the addition of oxygen thereto so that it will support aquatic life.

As is well known in the art to which my invention relates, the eliluent from sulphate paper mills is highly injurious to streams and its disposal has become a major industrial problem. The socalled sulphate soap" which accompanies the black liquor content in the effluent is highly toxic to aquatic life, as little as ve parts per million being suilicient to kill fish. As is also well known, the major part of the black liquor from the digesters in ,a sulphate process paper mill is separated from' the pulp after cooking, and is evaporated down to reduce the water content. It is.

then burned to furnish heat and to recover the l soda content which is used for cooking succeeding batches of wood. Considerable black liquor necessarily remains in the pulp after this operation, which black liquor is washed out and the resulting wash water must be disposed of. This wash water is further diluted by boiler blowdown water and other paper mili wastes, and constitutes the highly objectionable, toxic eiiluent which my process renders harmless'. I

The black liquor and sulphate soap in the effluent contain sodium lignate, sodium resinate,

sodium oleate, sodium hydroxy valerate. and ,sodium salts of other lactone and sugar acids. The eiliuent also contains calcium carbonate, pulp fiber, raw and partially cooked chips, bleachery wastes, and other waste products of the mill.

In accordance with my process, I inoculate the efliuent with cellulosev destroying micro-organisms, such as yeast, anaerobic bacteria, such as Actinomyces, or the cellulose destroying bacteria contained in ordinary barnyard manure and rotted wood. A culture such as described destroys the cellulose and lactone acids in the eiiiiient,

producing other acids or acid gases, such as carcentrifugal force, or other mechanical separation of the solids, to form a greatly improved product, so fares potability, color, appearance and effect on aquatic life isconcerned.

It is also contemplated, in accordance with my process, to add oxygen to the treated eiiiuent so as to render it more adaptable to support fish life. This may be accomplished by means of aeration, plant life, algae, or chemical treatment.

The single sheet of drawing hereto annexed and forming a part of this application illustrates diagrammatically in Fig. 1 the plan view of a typical means for carrying out my improved process, and in Fig. 2 a longitudinal sectional view.

Bygway of example, and referring to the drawing, the following description sets forth .the process employed by me in treating the eiiiuent from a ton sulphate process pulp and paper mill, the effluent of which consisted of wash water, black liquor, pulp ber, sulphate soap, partiaiiy cooked chips, alum solution, boiler blowdown, and other wastes. I first provide two connecting treatment ponds or reservoirs, one of which is .Y indicated on the drawing as a fermentation pond,

and the other la sedimentation pond, through which the eiliuent flows on its way to final discharge into a sewer or stream. While the process lose and precipitate the iignin and fatty and resinic acids from the eiiiuen assaoio make these ponds much larger than indicated,

for the reason that the longerthe eilluent is treated in `accordance with my process, the more satisfactory the results. I'he eiiluent from the mill is run continuously into-the fermentation pond while the mill is in' operation. I provide also a micro-organism makeup pond which discharges continuously into the stream of efliuent on its way to the fermentation pond. In the micro-organism makeup pond I may provide 50 pounds of potatoes and one pound of bakers yeast, which may be replenishedr as used up. I havefound that this provides a constant vsupply of micro-organisms sufficient to act upon the fiber, partially cooked chips, and lactonic acids of the black liquor, destroyingl them with theevollution of carbonio 'and other acids. The acids thus formed in turn neutralize the sodium lignate, sodium resinate, and sodium oleate of the black liquor and sulphate soap, and precipitate lignin, resins, and oleic acids in the fermentation pond.

By the time the body of eiliuent reaches the discharge end of the fermentation pond, the reaction ,is complete and the major portion of the solids are settled out. Leaving the fermentation pond, the eiiluent passes over an aerating cascide 'into the sedimentation pond, where the final setjAlso, as is obvious, ponds require less frequent cleaning.

tling out of solids occurs. The clarified effluent then passes over a second cascade dam for further ,aeration before being discharged into a.

stream. Plant life or algae is preferably provided in the-sedimentation pond to further increase the oxygen content of the effluent before .it is finally discharged, in order that it may be better adapted to support sh life.

Where readily obtainable, I prefer to add `other cellulose-destroying micro-organisms to the effluent on its way to the fermentation pond. For this purpose, Clostridium dissoluens, Actinomyces, or the cellulose destroying micro-organisms of common barnyard manure and from rotted wood may be employed. It is particularly important that the microorganisms be constantly added to the effluent as it enters the fermentation pond because, I have found, by the time the eflluent has reached they outlet to the sedimentation pond, the micro-organisms have died. The moving stream of effluent carries the micro-organisms down withit, and in order to keep the upper end 'of the fermentation pond inoculated, microorganisms must be constantly added.

Where the paper mill employingfmy process has a bleaching plant, it will be found to be an aid, rather than a detrimentyto the carrying out of the process.

The eiiluent after being partially clarified in the fermentation pond as here' inbefore described, may have added thereto the bleachery waste containing calcium chloride and traces of hypoehlorite. The calcium chloride precipitates as calciumv lignate any remaining sodium-lignate in solution, and the hypochlorite material reduces the oxygen demand of the solu- `tion. The precipitate formed by this reaction is `then allowed to settle out inthe sedimentation' pond. Obviously the fermentation pond and sedimentation pond will gradually accumulate solids and must be cleaned out at intervals, de-

pending up'on their original capacities. As before lremarked, vwhere land is available, it is preferable to employ large ponds for the collection and treatment of the effluent, as such afford a greater `time for treatment, a greater opportunity for `clarication and the settling out of precipitated solids, and the addition vof oxygen to the eiiluent.

` the eilluent.

line processes. Both processesdepend upon the dissolving action of caustic soda on the .non-v fibrous matter in wood.' Hence, much that can besaid of one process can be said in equal force and in the same language of the other.. When referred to separately, one is called the' Soda processand the other the Sulphate processq While I have` described but one form of my "invention, it will be obvious to those skilled in the art that it is not so limited,4 but is susceptible of various changes and modifications, without departing from the spirit thereof. and I desire, therefore, that only such limitations shall be 1 placed thereupon as are specifically set forth in the appended claims.

What I claim is: 1. 'Ihe method of treating the dilute alkaline black liquor containing eiiluent from a paper mill lwhich comprises passing it through. a storage reservoir having a. capacity sufficient to hold at least the total eiiiuent from a 24 hour run of the mill', and inoculatlng the eiiluent as it enters the reservoir with liquor containing cellulose and lactone acid destroying microorganisms having the property of producing carbon dioxide and other acidic substances and thereby causing the precipitation of lignin, fatty acids and resins from 2. The method of treating the dilute alkaline black liquor containing eilluent from a paper mill ervoir having a capacity sumcient to hold at least the total eiiluent from a 24 hour run of the mill,

, inoculatlng the eilluent as it enters the reservoir with liquor containing cellulose and lactone acid destroying microorganismshaving the property j of producingcarbon dioxide and'other acidic'substances and thereby causing the precipitation of lignin, fatty acids and` resins from the eiiluent, clarifying the thus treated eilluent, and adding oxygen thereto.

3. The method of treating the dilute alkaline black liquor containing eilluent from a paper mill which comprises passingit through a storage resi ervoir having a capacity sufficient to hold at least the total eflluent froma 24 hour run of the mill, inoculatlng the eflluent as it enters the reservoir with liquor containing cellulose and lactone acid destroying microorganisms selected from those found in yeast, barnyard manure and rotted wood and having the property of producing 'carbon dioxide and other acidic substances and thereby causing the precipitation of lignin, fatty acids and resins and clarifying the thus treated eiliuent, and adding oxygen thereto.

4.' Themethod of treating the'dilute 'alkaline black liquor containing ellluent from a paper mill which comprises passing it through a storage reservoir having a lminimum capacity suiicient to hold the total effluent from a 24 hour run of the mill, inoculatlng the eiiluent as it enters the res` ervoir with liquox` containing the microorganisms found in yeast and other cellulose and sugar destroying organisms having the property of producing carbon dioxide and other acidic substances to further clarify it, and adding oxygen thereto.

5. 'I'he method of treating the dilute alkaline black liquor containing effluent ,from a paper mill which comprises'passing itth-rough a storage reservoir having a capacity sufcient to hold the total eiliuent from a 24 hour run of the mill, inoculating the eilluent as it enters the resvoir with liquor containing the microorganisms found in yeast and other cellulose and sugar destroying organisms having the property of producing carbon dioxide and other lacidic subaerating it to add oxygen thereto, conducting the thus clarified eiiluent through a second storage reservoir, adding further oxygen adding agents thereto, allowing the eiiiuent l to go to waste, aerating the eiliuent asit goes to waste, and periodically removing precipitated substances from the reservoirs. v

8. The method of purifying the alkaline black liquor containing eflluen'. fromv a sulphate proccess paper mill which comprises passing the eiiluent in sequence through a plurality of treatment reservoirs the first of lwhich in the series'has a stances and thereby causing the precipitation of lignin, fatty acids and resins and clarifying the eiiiuent, adding calcium chloride to' the thus treated effluent to further clarify it, and aerating to increase the oxygen content thereof.

6. The method of treating the dilute alkaline black liquor containing effluent from a paper mill which comprises passing it through a storage res,- ervoir having a minimum capacity sufilcient to i hold the total eilluent from a 24 hour run of the mill, inoculating the effluent as it enters the reservoir with liquor containing the microorganisms found in yeast and other cellulose and sugar dey stroying organisms having the property of producing carbon dioxide and other acidic substances and thereby causing the precipitation of lignin, fatty acids and resinsY and clarifying the eiliuent, adding calcium chloride to the thus treated eilluent to further clarify it, separating the claried eflluent from theprecipitate, and aerating to increase the oxygen content thereof.-

7. The method of treating the dilute alkaline black liquor containing eiiiuent from a paper mill which comprises conducting the eilluent through a storage reservoir having a capacity sumclent to hold at least the eluent from a 24 hour run of the mill, inoculating the eiiluent as it enters the reservoir with liquor containing the microorganisms found in yeast, allowing the lignin, fatty acids and resins to precipitate, separating the thus treated effluent from the precipltteand minimum capacity sumcient to accommodate the emuent resulting from 24 hours operation of the mill, continuously adding liquor containing the microorganisms found in yeast to the effluent entering the first reservoir in the series to bring about a neutralization of the alkaline compounds in the eilluent and a precipitation of the lignin and fatty acids, aerating the eilluent as it passes from one reservoir to another to add oxygen thereto, adding plant life to the effluent before its final discharge to further increase the oxygen content thereof, further aerating before final discharge, 'and periodically removing precipitated material from the reservoirs.

9. The method of purifying the alkaline black liquor containing effluent from a sulphate process paper mill which comprises passing the emu- ,ent in sequence through a plurality of rtreatment reservoirs, the first of which in the series has a minimum capacity to-accommodate the eflluent resulting from 24 hours operation of the mill, continuously adding liquor containing the microorganismsfond in yeast to the effluent interposing plant life in the eiiluent in one of said reservoirs `after the first "in the series to in' crease the oxygen content thereto before' ilnal' discharge.

PAUL HODGES. 

